Electrostatically driven latchable actuator system

ABSTRACT

An electrostatically driven latchable actuator system has an actuator and a pair of side effectors on opposite ends of the actuator. The actuator is resiliently supported to a substrate and is movable along a linear axis between two operative positions as being electrically attracted to one of the side effectors. A latch mechanism is provided to mechanically latch the actuator at either of the operative positions. The side effectors are movably towards and away from the actuator along the linear axis between a normal position and a shifted position close to the actuator. Both of the side effectors are also resiliently supported to the substrate to be movable towards the actuator by being electrostatically attracted thereto and away from the actuator by resiliency. The moving side effector is interlocked to the latch mechanism through a mechanical link so as to unlatch the actuator in response to one of the side effectors being attracted to the actuator, and allow the actuator to move from one operative position to the other operative position to be again latched thereat.

TECHNICAL FIELD

The present invention is directed to an electrostatically drivenlatchable actuator system, and more particularly to the latchableactuator system of a type fabricated as the MEMS(Micro-Electro-Mechanical Systems).

BACKGROUND ART

US Patent Publication 2002-0102059 A1 discloses a prior art actuatorsystem fabricated on a silicon substrate as the micro-electro-mechanicalsystem for switching an optical path. The system includes an actuatorcarrying a shutter which selectively interrupts an optical path. Theactuator is movably supported to the substrate and is formed with anelectrode which is cooperative with a driving electrode fixed on thesubstrate to develop an electrostatically attracting force therebetweenfor shifting the actuator between two operative positions, one is anON-position of receding the shutter from the optical path and the otheris an OFF-position of projecting the shutter into the optical path. Amechanical latch is provided in the system to latch the actuator in theOFF-position. For this purpose, the actuator is formed at its one endwith a catch which comes into latching engagement with dents when theactuator moves into the OFF-position. The dents are formed respectivelyat the ends of latching electrodes which are additionally incorporatedon the substrate. Further, In order to unlatch the actuator, the systemrequires additional driving electrodes for driving the latchingelectrodes to move it electrostatically for disengaging the detents fromthe catch of the actuator. Thus, unlatching of the actuator isaccomplished in the prior art system by introducing an additional set ofelectrodes other than those designed to drive the actuator itself. Theinclusion of the additional electrodes largely detracts from the conceptof the MEMS of giving a micro-structure, and would be more critical whenthe actuator is required to be latched not only in the OFF-position butalso in the ON-position since it requires a further set of electrodesfor latching the actuator in the ON-position.

DISCLOSURE OF THE INVENTION

In view of the above problem, the present invention has been achieved toprovide a unique latchable actuator system which is capable of latchingthe actuator without requiring an additional set of electrodes, i.e., bymaking the best use of electrodes essential to the operation of theactuator. The actuator system of the present invention includes asubstrate carrying an actuator which is movable along a linear axisbetween two operative positions past a neutral position. The actuator isadapted in use to be connected to drive an object for shifting theobject. The actuator is formed on its opposite ends respectively withcenter electrodes with respect to the linear axis, and is resilientlysupported to the substrate to be given a spring bias by which theactuator is urged towards the neutral position. Also formed on thesubstrate are first and second side effectors which are disposedrespectively on the opposite ends of the actuator with respect to thelinear axis, and which are provided respectively with side electrodesthat are held in electrostatically coupling relation with the adjacentcenter electrodes. A driving means is included in the system to developan electrostatically attracting force between the center electrodes andthe side electrodes for driving the actuator into either one of the twooperating position. Also, the system includes latch means for latchingthe actuator in one of the operative positions, and unlatch means forunlatching the actuator to allow it to move out of said one operativeposition to the other position. The characterizing feature of thepresent invention resides in that the side effectors are movably towardsand away from the actuator along the linear axis between a normalposition and a shifted position close to the actuator, and that theunlatch means is interlocked with the movement of the side effectors inorder to unlatch the actuator in response to one of the side effectorsmoving to its shifted position from the normal position, therebyallowing the actuator to move to the other operative position byelectrostatically attracting force developed between the one of the sideeffectors and the actuator. With this arrangement, the side effectorsact not only to move the actuator between the operative positions, butalso acts to unlatch the actuator, realizing the latchable actuatorsystem without requiring additional electrodes and therefore making itpossible to arrange the system of a micro structure.

Preferably, the latch means is composed of catches formed respectivelyat opposite ends of the actuator and latch members formed on thesubstrate respectively adjacent to the side effectors. Each latch memberhas a detent engageable with the associated one of the catches of theactuator. Each catch takes two conditions in response to the movement ofthe actuator, i.e. latch-enabled condition where the catch is engageablewith the detent for latching the actuator, and a latch-disabledcondition where the catch is kept free from engageable with the detent.The actuator is disposed in such a relation with the latch member thatone of the catches is held in the latch-disabled position when the othercatch is in the latch-enabled position. That is, each one of thecatches, in response to the movement of the actuator, comes into thelatch-enabled position from the latch-enabled position so as to be heldin latching engagement with the associated detent. The unlatch meansincludes a release links each mechanically coupling each one of the sideeffectors to each associated one of the latch members. Thus, eachrelease links acts to move each corresponding one of the latch membersforcibly for releasing the engagement of the detent with the catch, inresponse to the associated side effector moving to the shifted position,thereby unlatching said actuator. The release link may be realized byone or more springs formed on the substrate.

The latch members are preferred to be isolated electrically from theside electrodes for successfully applying the intended voltagedifference across one or both of the side electrodes and the centerelectrodes.

The latch member is resiliently supported to the substrate to be movablebetween a latching position of engaging the detent with the associatedcatch in the latch-enabled condition, and a releasing position ofreleasing the detents from the catch in the latch-enabled condition.Thus, after the catch moves into the latch-enabled condition inconsequence of the actuator movement, the latch member returns to thelatching position for immediate latching the actuator in the operativeposition.

In a preferred embodiment, the system is designed such that both of thecatches are held in the latch-disabled position when the actuator is inits neutral position. As the one side effector moves to the shiftedposition, the associated one of the release links forces the latchmember into the release position and allows the catch that has been heldin the latch-enabled condition to move into the latch-disabledcondition, thereby unlatching the actuator and permitting it to move outfrom the one operative position. Further, each one of the caches is madeengageable with the associated one of the latch members so as to forceit to move from the latching position to the releasing position, inresponse to the actuator moving in a direction of being unlatched at theother catch, whereby the one catch is allowed to move from thelatch-disabled condition to the latch-enabled condition for latchingengagement with the latch member resiliently returning to the latchingposition. In this manner, when the latch member is driven by theadjacent side effector to unlatch the actuator at its one end, i.e.,disengage the detent from the catch at that end, the catch istransferred into the latch-disabled condition in consequence of theresulting actuator movement, while the other catch is transferred intothe latch-enabled condition to be ready for coming into the latchingengagement with the associated latch member. Therefore, the actuator canbe latched both at the two operative positions.

For driving the actuator into one of the operative positions from theneutral position, the driving means is configured to apply a voltagedifference between the side electrodes of one of said side effectors andthe center electrodes of the actuator. Likewise, for moving the actuatorfrom each one of the operative positions to the other operativeposition, the like voltage difference is applied between the electrodeof the one side effector and the center electrode. Further, for movingthe actuator from any one of the operative positions to the neutralposition, the voltage difference is applied between the side electrodesof the both side effectors and the center electrodes of the actuator.

In another preferred embodiment, the latch means additionally includesretainer means to hold the actuator around the neutral position in theabsence of the electrostatically attracting force. Thus, the actuatorcan be stable at any one of the two operative positions and the neutralposition, and accordingly give a tri-stable actuator system.

The latch means may be so designed to have a combination of at least onelatch member resiliently supported to the substrate in an adjacentrelation to each side effector, and a socket formed at each opposite endof the actuator. The latch member is fixed at its one end to thesubstrate and is formed at the other free end with a detent. The socketis shaped to releasably receive the detent and is formed at its open endwith a catch engageable with the detent. When the actuator is in eitherone of the operative positions, one of the catches abuts against thedetent outside of the socket for latching the actuator in this position.When the actuator moves out from one of the operative positions by beingelectrostatically attracted to one of the side effectors with one of thecatches unlatched, the other catch at the opposite end of the actuatorbecomes engaged with the detent inside of the socket to resilientlydeform the latch member, allowing the detent to escape outwardly of thesocket. Thus, the latch member is permitted to return by its ownresilience to be ready for the latching engagement with the catchoutside of the socket after the actuator moves to the other operativeposition. In this instance, the unlatch member includes a release leverformed at each of the side effectors to be movable together therewith.The release lever is engageable with the latch member to constitute amechanical link between the side effector and the latch member. When therelease lever engages with the latch member in response to theassociated side effector moving to the shifted position, it deforms thelatch member for releasing the detent from the catch to thereby unlatchthe actuator and allows the dent to advance it into the socket, enablingthe actuator movement from the one operative position to the otheroperative position.

Preferably, each of the socket is formed in its interior with a retainerprojection spaced inwardly from the catch along the linear axis. Theretainer projection is held close to the catch when the actuator is inthe neutral position, thereby retaining the actuator around its neutralposition in the absence of the electrostatically attracting force andtherefore hold the actuator stably also in the neutral position.

The above latchable actuator system may be well incorporated into anoptical switch having an input optical guide adapted to receive a lightsignal, and at least two output optical guides each adapted to outputthe light signal. The actuator of the system is connected to a mirrorreflecting the light signal incoming through the input optical guide fortransmitting the light signal selectively to one of the output opticalguides. Since the actuator system can be designed to a compact structurewith the latching capability, the optical switch can be also madecompact, yet be given a reliable switching function.

These and still other advantageous features of the present inventionwill become more apparent from the following detailed description of thepreferred embodiments when taken in conjunction with the attacheddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an actuator system in accordance with afirst embodiment of the present invention where the system isincorporated into an optical switch;

FIG. 2 is a top view of the optical switch incorporating the actuatorsystem on a common substrate;

FIG. 3 is an enlarged view of a portion of the optical switch;

FIG. 4 is a plan view of the actuator system shown with an actuator inits neutral position;

FIG. 5 is a sectional view of a part of the actuator system illustratingthe MEMS technology by which the actuator system is fabricated;

FIG. 6 is a partial perspective view of a part of the actuator system;

FIGS. 7 to 10 are respectively plan views illustrating the actuatormovement from its neutral position to right operative position;

FIGS. 11 to 14 are respectively plan views illustrating the actuatormovement from the right operative position to a left operative position;

FIGS. 15 to 17 are respectively plan views illustrating the actuatormovement from the left operative position to the neutral position;

FIG. 18 is a plan view of an actuator system in accordance with a secondembodiment of the present invention;

FIGS. 19 to 22 are respectively plan views illustrating the actuatormovement of the above actuator system from its neutral position to leftoperative position;

FIGS. 23 to 28 are respectively plan views illustrating the actuatormovement from the left operative position to right operative position;and

FIGS. 29 to 32 are respectively plan views illustrating the actuatormovement from the right position to the neutral position.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring to FIGS. 1 to 3, there is shown an optical switch 200 as oneexample in which an actuator system of the present invention isincorporated. The actuator system has an actuator which is utilized inthe optical switch 200 for switching an incoming light signal toselective one of output optical guides 302 and 303. The optical switch200 includes an integrated chip 300 fabricated into a micro-structure bya method generally referred to as MEMS (micro-electro-mechanical system)technology. The chip 300 includes the actuator system S as explained indetail hereinafter, and a set of electrodes 330 for energization of theactuator system, in addition to an input light guide 301 and the twooutput optical guides 302 and 303, as shown in FIG. 2. The opticalguides receive respective optical fibers 360 leading to and from anoptical fiber network.

As shown in FIG. 3, the input and output optical guides are arranged tohave their ends gathered to a switch yard 308 together with two mirrors322 and 323. One 322 of the mirrors is fixed to reflect the incominglight signal to the first output optical guide 302, while the othermirror 323 is connected to the actuator 20 of the actuator system to bemovable between a reflecting position of reflecting the incoming lightsignal to the associated output light guide and a retracted position ofdisabling the reflection to the associated output light guide. Thus, thelight signal is switched to the selected one of the output light guidesby energizing or deenergizing the actuator system. The mirror is latchedin either position after the actuator system is deenergized. As shown inFIG. 1, the chip 300 is accommodated within a casing 340 together with aprinted board 350 forming a control circuit for driving the actuatorsystem. The casing 340 is provided with connectors for connection ofoptical fibers 360 respectively to the input optical guide 301 and theoutput optical guides 302 and 303. It should be noted here that theabove optical switch is illustrated only as one application of theactuator system, and therefore the actuator system of the presentinvention can be utilized in many other applications where the actuatoris required to be latched.

FIRST EMBODIMENT <FIGS. 4 TO 17>

Now, the actuator system of the present invention is explained indetail. As shown in FIGS. 4 to 6, the actuator system is composed ofmovable components movably supported on a silicon substrate 10, andfixed components formed on the substrate 10 for resiliently supportingthe movable components by means of springs, ones of the movablecomponents. The movable and fixed components are also made from siliconby the MEMS technology. The movable components include a single actuator20 movable along a linear axis and a pair of side effectors 50 disposedin a spaced relation from the opposite ends of the actuator 20, as shownin FIG. 4. The actuator 20 is supported to center posts 40, the fixedcomponents, by means of springs 41 to be movable between two operativepositions, and is urged to neutral position of FIG. 4 by the bias of thesprings 41. The actuator 20 is integrally formed on its opposite endswith comb-shaped center electrodes 22, and also with an extension arm 24carrying the mirror 323. Each side effector 50 is supported to sideposts 60, the fixed components, by means of springs 61 to be movablealong the linear axis between a normal position and a shifted positionoffset centrally along the linear axis from the normal position, and isbiased towards the normal position by the bias of the springs 61. Eachof the side effectors 50 is also provided with comb-shaped sideelectrode 52 which are held in an intermeshing relation with theadjacent center electrode 22 to develop an electrically attracting forcetherebetween. The movable and fixed components are arranged in a layeron the substrate 10 as shown in FIG. 5. In this connection, thesubstrate 10 is formed on its top with raised platforms 12 to leaverecesses 14 in the remainder of the top. The fixed components aredeposited on the raised platforms 12, while the movable components areheld in a spaced relation respectively with the bottoms of the recesses14 and are supported to the fixed components on the platforms 12 eitherdirectly or indirectly through the one or more of the other movablecomponents, as schematically shown in FIG. 6. It is note that FIGS. 5and 6 are given only for illustrating the layered structure as well as ageneralized interconnection of the fixed and movable components, but donot reflect actual geometrical configuration of the components shown inFIG. 4.

Each of the center posts 40 is connected to the actuator 20 by the foursprings 41 and a floating joint 42. The four springs are disposed ingenerally parallel relation with each other when the actuator 20 is inits neutral position with two inner springs 41 bridging across thecenter post 40 and the joint 42, and also with the other two outersprings 41 bridging across the joint 42 and the actuator 20, in order toelongate an effective spring length for giving a relatively long stroketo the axial movement of the actuator 20. Likewise, each side post 60 isconnected to the side effector 50 by the four springs 61 and a floatingjoint 62 with two outer springs 61 bridging across the side post 60 andthe joint 62, and also with the other two springs 61 bridging across thejoint 62 and the side effector 50, in order to give a relatively longstroke to the axial movement of the side effector 50.

Also included in the movable components are latch members 70 each ofwhich is disposed within a frame of the side effector 50 to constitute alatch mechanism, in combination with a catch 30 each formed at theopposite ends of the actuator 20, for latching the actuator in either ofthe operative positions. Each latch member 70 is movable in a directionperpendicular to the linear axis between a latching position of latchingthe actuator 20 in one of its operative positions and a releasingposition of unlatching the actuator. Each latch member 70 is resilientlysupported to an end post 80 by means of springs 81 to be urged therebytowards the latching position, and is also coupled to the adjacent sideeffector 50 by means of springs 54. The springs 54 define a release linkwhich interlocks the latch member 70 with the movement of the associatedside effector 50 for unlatching the actuator 20 as will be latediscussed in detail. In short, the movable side effector 50 and therelease link 54 is cooperative to constitute an unlatch mechanism forreleasing the latch members 70 to thereby unlatch the actuator 20 andallow it to move from one of the operative position to the otheroperative position. Although each of the latch members 70 is held in thelatching position when the actuator 20 is in the neutral position ofFIG. 4, the actuator 20 is not latched in this position, as will beexplained later.

The actuator 20 includes a center beam 26 extending along the linearaxis and being formed at its opposite ends respectively with the catches30 each in the form of a ratchet tooth. Each catch 30 is shaped to haverear vertical edges 32 responsible for latching engagement with detent72 at the tip of the latch member 70 and inclined edges 34 sloping downfrom the rear edges to the beam 26 to be engageable with the detent 72of the latch member 70. The catch 30 comes into the latching engagementwith the detents 72 when the actuator 20 is in one of the operativepositions, as shown at the left-hand latch members 70 in FIG. 10,thereby latching the actuator in this position. The inclined edges 34come into sliding engagement with the detents 72, when the actuator 20is moving from the neutral position to one of the operative position orfrom one of the operative position to the other operative position, asshown at the left-hand catch 30 in FIG. 7 and at the right-hand catch 30of FIG. 12, such that the latch members 70 are forced to retract fromthe latching position to the releasing position, allowing the catch 30to move axially inside of the latch members 70 and making the latchmembers 70 to be ready for the latching engagement with the catch 30.

Details of the latching actions will be explained in relation to theaxial movement of the actuator 20 with reference to FIGS. 4 and 7 to 17.For the sake of understanding rather complicated operations of the latchmechanism, it is first mentioned that the catch 30 assumes differentconditions which are different from different positions of the actuator20 and that the catch 30 is held in a latch-disabled condition where itis kept axially outwardly of the latch members 70 to be unable to belatched thereby as shown in FIG. 4, and is held in a latch-enabledcondition, as seen in the left-hand catch 30 in FIG. 8 and in theright-hand catch 30 in FIG. 13, where it comes axially inside of thelatch members 70 so as to be capable of being latched at its rearvertical edges 32 with the latch member 70 returning to the latchingposition.

The latching actions are now explained in relation to three actuatormovements. The actuator 20 is caused to move between the two operativepositions by a driving means or circuit which applies a voltagedifference across a selected combination of the electrodes. The voltagedifference can be given, for example, by electrically charging eitherone or both of the side effectors, i.e., the side electrodes, whilegrounding the actuator, i.e., the center electrodes. For the sake ofbetter understanding of the operations with reference to the drawings,the parts being energized or electrically charged are indicated bycrossing lines in the figures. As seen in the figures, the sideelectrodes 52 are charged through respective posts 60 and the springs61. Further, since the side electrodes and the center electrodes areintegrally formed respectively with the side effector and the actuator,the side effector and the actuator are simply referred to in thedescription whenever their electrodes are electrically charged orapplied with the voltage difference.

(1) Neutral Position to One of Two Operative Positions <FIGS. 4, and 7to 10>.

Firstly, the voltage difference is applied only across the right-handside effector 50 and the actuator 20 in its neutral position of FIG. 4,to develop an electrostatically attracting force between the right-handside effector 50 and the actuator 20, moving them towards to each otheras indicated by arrows in FIG. 7. In this consequence, the left-handcatch 30 comes into engagement with the latch members 70 to force ittowards the releasing position against the bias of the springs 81. Atthis time, the right-hand catch 30 is kept in the latch-disabledcondition. As the actuator 20 moves further to the most-right end ofFIG. 8, where it is closest to the side effector 50 moved to its shiftedposition, the left-hand catch 30 advances to its latch-enabledcondition, while the left-hand latch members 70 return to their latchingposition by the bias of the springs 81 so as to be ready for latchingthe actuator 20 at the left-hand catch 30. Upon subsequentdeenergization of the right-hand side effector 50, i.e., removal of theelectrostatically attracting force, the actuator 20 is caused to moveback by the bias of the springs 41 to only a slightest extent until theleft-hand catch 30 abuts against the detents 72 of the latch members 70already returned to the latching position, as shown in FIG. 9, therebylatching the actuator 20 in the right operative position to keep it frommoving back toward the neutral position. At the same time, theright-hand side effector 50 moves back to the normal position as show inFIG. 10, with the actuator 20 is kept latched at the left-hand catch 30and with the right-hand catch 30 held in the latch-disabled condition.

(2) Right Operative Position of Left Operative Position <FIGS. 11 to 14>

The voltage difference is applied only across the left-hand sideeffector 50 and the actuator 20, in order to electrostatically attractthe left-hand side effector 50 and the actuator 20 to each other. As aresult of the left-hand side effector 50 moving to the shifted position,as shown in FIG. 11, it forces the associated latch members 70 throughthe release link or the springs 54 to move the latch members 70 into thereleasing position against the bias of the springs 81. Thus, theactuator 20 is allowed to move to the left by the electrostaticallyattracting force. As the actuator 20 moves further to a position of FIG.12, the right-hand catch 30 at the rear moving end of the actuator 20comes into engagement at its inclined edges 34 with the associated latchmembers 70 to force them into the releasing position, thereby permittingthe further actuator movement with attendant movement of the catch 30 atthe rear moving end of the actuator into the latch-enabled condition.During this movement, the catch 30 at the front moving end of theactuator goes into the latch-disabled condition. When the actuator 20moves further to be closest to the left-hand side effector 50, as shownin FIG. 13, the right-hand latch members 70 return to the latchingposition by the springs 81 so as to be ready for the latching engagementwith the catch 30 at the rear moving end of the actuator 20. Uponsubsequent removal of the electrostatically attracting force, theactuator 20 moves back by the bias of the springs 41 to a slightestextent until the right-hand catch 30 comes into abutment against thelatch members 70, as shown in FIG. 14, thereby latching the actuator 20in the left operative position. Simultaneously, the left-hand sideeffector 50 returns to its normal position by the bias of the springs 51with the left-hand catch 30 being kept in the latch-disabled condition.In the like manner, the actuator 20 is caused to move from the leftoperative position to the right operative position to be latched thereatby firstly applying the voltage difference only across the right-handside effector 50 and the actuator 20 followed by removing the voltagedifference.

(3) Left Operative Position to the Neutral Position <FIGS. 15 to 17>

The voltage difference is applied across the two side effectors 50 andthe actuator 20, in order to move both side effectors 50 towards theactuator 20 by the electrostatically attracting forces, as shown in FIG.15. Upon this occurrence, the right-hand side effector 50 moves to theshifted position to force the latch members 70 into the releasingposition, thereby unlatching the actuator 20 and allowing it to move tothe right by the bias of the springs 41 as well as the balancingelectrostatic attracting forces. As the actuator 20 moves further intothe neutral position, as shown in FIG. 16, with both of the sideeffectors 50 being kept in the shifted positions, the left- andright-hand catches 30 are held in the latch-disabled condition. Afterremoval of the electrostatically attracting forces, both of the sideeffectors 50 are returning to the normal position by the bias of thesprings 61 and allowing the left- and right-hand latch members 70 toreturn to the latching position but not in actual latching engagementwith the corresponding catches 30, as shown in FIG. 17. Then, theactuator 20 is kept at the neutral position of FIG. 4 by the bias of thesprings 41. In this sense, the illustrated actuator system gives theactuator which is a held at either of three positions and mechanicallylatched at either of two operative positions. Although not specificallymentioned in the above explanation of the latching actions, the springs54 also act to move the side effector 50 back to the normal position incooperation with the resiliently returning movement of the latch members70 to the latching position, after the electrostatically attractingforce is removed from the side effector 50.

It is noted in this connection that each side post 60 connected to eachside effector 50 is electrically isolated from the center posts 40coupled through the springs 41 to the actuator 20 in order tosuccessfully apply the intended voltage difference across one or both ofthe side effectors 50 and the actuator 20. In addition, each sideeffector 50 is formed with dielectric section 58 which isolates thelatch members 70 electrically from the associate side effector 50,thereby keeping the actuator 20 from conducting electrically to the sideeffector 50 through the latch members 70 and therefore assuring to applythe intended voltage difference between the side effector 50 and theactuator 20.

SECOND EMBODIMENT <FIGS. 18 TO 32>

FIGS. 18 to 33 illustrate another actuator system in accordance with asecond embodiment of the present invention, which is similar to thefirst embodiment except for the details of the latching mechanism.Accordingly, no duplicate explanation is deemed necessary for thedetails of the basic structures of the system. The system includes anactuator 120 and a pair of side effectors 150 as in the aboveembodiment. The actuator 120 is integrally formed with the likecomb-shaped center electrodes 122 and is resiliently supported to thecenter posts 140 by means of springs 141 to be movable along a linearaxis between two operative positions past a neutral position against thebias of the springs 141. Each of the side effectors 150 located onopposite ends of the actuator 120 is integrally formed with likecom-shaped side electrodes 152, and is resiliently supported to the sideposts 160 by means of springs 161 to be movable along the linear axisbetween a normal or unbiased position and a shifted position close tothe actuator 120.

Also in this embodiment, two latching mechanisms are providedrespectively on opposite ends of the actuator 120 for latching it ineither of the two operative positions. Each latching mechanism includesa latch member 170, and a socket 130 on each opposite end of theactuator 120. The latch member 170 is coupled to an end post 180, thefixed component on the substrate 10, and is shaped into a generallyU-shaped configuration with a pair of resilient legs 171 connected by aweb 173 at which the latch member 170 is supported to the end post 180.The resilient legs 171 are resiliently deformable to assume twopositions, one is a latching position where the resilient legs 171 runsparallel to each other without being deformed, as seen at the right-handlatch member 170 in FIG. 22, and a releasing position where theresilient legs 171 are deformed or collapsed to come close to eachother, as seen at the right-hand latch member 170 in FIG. 23. Eachresilient leg 171 is formed with a detent 172 at its distal end forlatching engagement with the outer end of the socket 130 s seen at theright-hand latch member 170 in FIG. 22.

Each resilient leg 171 is formed with a projection 174 which is spacedinwardly from the detent 172 to be engageable with a release lever 154formed on each of the side effectors 150, as shown at the left-handlatch member 170 in FIGS. 19 to 21. The release lever 154 establishes amechanical linkage between each of the side effectors 150 and theassociated one of the latch members 170, and is cooperative with themoving side effector 150 to define the unlatch mechanism for unlatchingthe actuator 120.

The socket 130 is formed integrally at each of the opposite ends of thecenter beam 126 of the actuator 120 to have an axial open end throughwhich the resilient legs 171 are allowed to advance into the interior ofthe socket 130, as shown at the right-hand socket 130 in FIGS. 24 to 27,for example. Inward projections are formed at the open end of the socket130 to define catches 132 which come into abutment with the detents 172of the latch member 170 when the resilient legs 171 comes out of thesocket 130, as shown at the right-hand socket 130 in FIG. 22, forexample. The socket 130 is also formed with retainer projections 134which are offset axially inwardly of the catches 132 to be in closelyadjacent relation to the detents 172 of the latch member 170 when theactuator 120 is in the neutral position of FIG. 18, for retaining orlocking the actuator 120 around the neutral position.

The latching actions of the second embodiment are now explained inrelation to three actuator movements.

(1) Neutral Position to Left Operative Position <FIGS. 18 to 22>

In the absence of the electrically attracting force, the actuator 120 isheld in the neutral position of FIG. 18 by being urged by the springs141 respectively connecting the actuator 120 to the center posts 140. Byapplying the voltage difference only across the left-hand side effector150 and the actuator 120, the actuator 120 starts moving to the left,and at the same time the left-hand side effector 150 starts moving movesto the right by the electrostatically attracting force, as shown in FIG.19. As the left-hand side effector 150 moves to the right, the releaselevers 154 press the projections 174 of the latch member 170 to therebydeform the resilient legs 171 into the releasing position and allow thelegs 171 to advance into the corresponding socket 130. With this result,the retainer projections 134 become free from interfering with thedetents 172. At the same time, the right-hand socket 130 moving to theleft becomes engaged at the catches 132 with the detents 172 of theassociated latch member 170, deforming or collapsing the resilient legs171 into the releasing position and consequently allowing the socket 130to be disengaged from the latch member 170. Thus, the actuator 120 ispermitted to move further to the left-most position of FIG. 20.Immediately thereafter, the resilient legs 171 of the right-hand latchmember 170 return or spring back to the latching position to be readyfor the latching engagement with the corresponding catches 132, as shownin FIG. 21. Upon removal of the electrostatically attracting force, theactuator 120 moves back to the right by the bias of the springs 141 onlyto a slightest extent until the catches 132 abut against the detents 172at the right-hand latch member 170, as shown in FIG. 22, and is latchedin this operative position. At the same time, the left-hand sideeffector 150 returns back by the bias of the springs 161 into the normalposition, as shown in FIG. 22, completing the actuator movement with thelatching of the actuator.

(2) Left Operative Position to Right Operative Position <FIGS. 23 to 28>

By applying the voltage difference across the right-hand side effector150 and the actuator 120, the right-hand side effector 150 starts movingto the left, as shown in FIG. 23, pressing the projections 174 on theresilient legs 171 by the release levers 154 to collapse the latchmember 170 into the releasing position. Thus, the actuator 120 isunlatched at the right-hand latch member 170, as shown in FIG. 24, andis ready to move to the right with the right-hand socket 130 receivingtherein the collapsed resilient legs 171. At the same time, theleft-hand socket 130, which is moving to the right, presses the detents172 at the retainer projections 134 to collapse the resilient legs 171into the releasing position, thereby being disengaged from the latchmember 170 for permitting the actuator 120 to move to the right. As theactuator 120 moves further to the right by being electrostaticallyattracted to the right-hand side effector 150, as shown in FIG. 25, theright-hand socket 130 keeps the resilient legs 171 collapsed byengagement of the retainer projections 134 with the detents 172. At thesame time, the left-hand socket 130 also keeps the resilient legs 171collapsed by engagement of the catches 132 with the detents 172, therebypermitting the actuator 120 to move further to the right-most positionof FIG. 26. In this condition, the resilient legs 171 of the left-handlatch member 170 are caused to escape out of the socket 130 and returnsto the lathing position to be ready for the latching engagement with thecatches 132 outside of the socket 130. Upon removal of the electrostaticattracting force, the actuator 120 moves back to the left by the bias ofthe springs 141 only to a slightest extent until the catches 132 abutagainst the detents 172 at the left-hand latch member 170, as shown inFIG. 27, and is latched in this operative position. Concurrently, theright-hand side effector 150 returns back by the bias of the springs 161into the normal position, as shown in FIG. 28, completing the actuatormovement to the right operative position with the latching of theactuator in this position.

(3) Right Operative Position to the Neutral Position <FIGS. 29 to 32,and FIG. 18>

Both of the side effectors 150 are electrically charged while groundingthe actuator 120 to give the voltage difference therebetween, i.e.,develop the electrostatically attracting forces in order to start movingboth of the side effectors 150 towards the actuator 120 in the rightoperative position, as shown in FIG. 29. In this consequence, theleft-hand side effector 150 presses the latch member 170 by the releaselevers 154 to collapse it into the releasing position, permitting theresilient legs 171 to advance into the socket 130, while the right-handside effector 150 presses the latch member 170 at the release levers 154to collapse it also into the releasing position, disengaging the detents172 from the retainer projections 134 and permitting the detents 172 tomove past the retainer projections. Whereby, the actuator 120 is allowedto move towards its neutral position by the bias of the springs 141 andthe balancing electrostatic attracting forces, as shown in FIG. 30.After the actuator 120 moves back to the neutral position, as shown inFIG. 31, the side effectors 150 are still held in the shifted positionas being electrostatically attracted to the actuator 120 to keep theresilient legs 171 of each latch member 170 collapsed into the releasingposition. Upon removal of the electrostatically attracting forces, bothof the side effectors 150 starts returning by the bias of the springs161 towards the normal position, as indicated by arrows in FIG. 32,while disengaging the release levers 154 from the projections 174 andpermitting the resilient legs 171 to return by their own resilience withthe detents 172 being kept confined within the sockets 130 thus, both ofthe side effectors 150 return to their normal or unbiased position,while keeping the actuator 120 in the neutral position, as shown in FIG.18. In this condition, the detents 172 on the latch members 170 are heldaxially outwardly of the retainer projections 134 in a closely adjacentrelation thereto, which serves to keep the actuator 120 around theneutral position in the absence of the electrostatically attractingforce, by the biasing force of the springs 141 and also by theengageable relation between the retainer projections 134 and the detents172.

Each of the side effectors 150 is formed with dielectric sections 158which isolate the latch members 170 electrically from the electrodes 152in order to avoid the latch members 170 from being electrically charged,thereby keeping the intended voltage difference across the side effector150 and the actuator 120 with which the latch member 170 comes into anelectrically conductive relation during the actuator movement. Althougheach of the side effectors 150 is illustrated in the figures to bedivided into two halves, the two halves may be mechanically andelectrically coupled to each other.

1. An electrostatically driven latchable actuator system comprising: asubstrate; an actuator carried on said substrate to be movable along alinear axis between two operative positions past a neutral position,said actuator being adapted to be connected to an object for shiftingthe object, said actuator being formed on its opposite ends respectivelywith center electrodes with respect to said linear axis, and beingresiliently supported to said substrate to be given a spring bias bywhich said actuator is biased towards said neutral position; first andsecond side effectors carried on said substrate and disposedrespectively on opposite ends of said actuator with respect to saidlinear axis; said side effectors being formed respectively with sideelectrodes that are held in electrostatically coupling relation withsaid center electrodes; driving means which develops anelectrostatically attracting force between said center electrode andsaid side electrodes for driving said actuator into either one of saidtwo operating position; latch means which latches said actuator in oneof said operative position against said spring bias when said actuatoris moved to said one position, and unlatch means which unlatches saidactuator to allow it to move out of said one operative position towardsthe other operative position, wherein said side effectors are movabletowards and away from said actuator along said linear axis between anormal position and a shifted position close to said actuator, saidunlatch means is interlocked with the movement of said side effectors inorder to unlatch said actuator as one of said side effectors moves to itshifted position, thereby allowing said actuator to move out of one ofsaid operative position and allowing it to move to the other operativeposition by the electrostatically attracting force developed betweensaid one side effector and said actuator.
 2. The system as set forth inclaim 1, wherein said latch means comprises: catches formed respectivelyat opposite ends of said actuator, and latch members formed on saidsubstrate respectively adjacent to said side effectors, each of saidlatch members having a detent engageable with the associated catch, eachof said catches assuming two conditions in response to the movement ofthe actuator, one being a latch-enabled condition where said catch isengageable with said detent for latching said actuator, and the otherbeing a latch-disabled condition where said catch is kept free fromengageable with said detent, one of said catches being in saidlatch-disabled position when the other catch is in said latch-enabledposition, each one of said catches, in response to the movement of saidactuator, coming into said latch-enabled position from saidlatch-enabled position so as to be held in latching engagement with theassociated detent, said unlatch means including release links eachmechanically coupling each one of said side effectors to each associatedone of said latch members, each of said release links forces eachcorresponding one of said latch members to move for releasing theengagement of said detent with said catch, in response to saidassociated one of said side effectors moving to said shifted position,thereby unlatching said actuator.
 3. The system as set forth in claim 2,wherein said release link comprises one or more springs formed on saidsubstrate.
 4. The system as set forth in claim 2, wherein said latchmembers are electrically isolated respectively from said sideelectrodes.
 5. The system as set forth in claim 2, wherein said latchmember is resiliently supported to said substrate to be movable betweena latching position of engaging said detent with the associated catch insaid latch-enabled condition, and a releasing position of releasing saiddetents from said catch in said latch-enabled condition.
 6. The systemas set forth in claim 5, wherein both of said catches are held in saidlatch-disabled condition when said actuator is in said neutral position,said release link, in response to the movement of the associated one ofsaid side effectors to its shifted position, forcing said latch memberinto said release position and allowing the associated one of saidcatches that has been held in said latch-enabled condition to move intosaid latch-disabled condition, thereby unlatching said actuator andpermitting it to move out from one of said operative position, each oneof said catches being engageable with the associated one of said latchmembers to force it to move from said latching position to the releasingposition as said actuator moves in a direction of being unlatched at theother catch, allowing said one catch to move from said latch-disabledcondition to said latch-enabled condition such that said latch memberresiliently returns thereafter to the latching position for making thelatching engagement with said one catch.
 7. The system as set forth inclaim 1, wherein said driving means is configured to apply a voltagedifference between the side electrode of one of said side effectors andsaid center electrodes for electrostatically attracting said actuator tosaid one side effector to move said actuator from said neutral positioninto one of said operative positions.
 8. The system as set forth inclaim 1, wherein said driving means configured to apply a voltagedifference between said side electrodes of one of said side effectorsand said center electrodes for electrostatically attracting saidactuator to said one side effector towards to move said actuator intoone of said operative positions from the other operative position. 9.The system as set forth in claim 1, wherein said driving meansconfigured to apply a voltage difference between said side electrodes ofsaid both side effectors and said center electrodes for moving saidactuator into said neutral position from anyone of said operativepositions.
 10. The system as set forth in claim 1, wherein said latchmeans includes retainer means which holds said actuator around saidneutral position in the absence of said electrostatically attractingforce between said actuator and any one of said side effectors.
 11. Thesystem as set forth in claim 1, wherein said latch means comprises: atleast one latch member resiliently supported to said substrate in anadjacent relation to each of said side effectors, said latch memberbeing fixed at its one end to said substrate and being formed at theother free end with a detent; a socket formed at each opposite end ofsaid actuator for releasably receiving said detent, said socket beingprovided at its open end with a catch engageable with said detent, oneof said catches abutting against said detent outside of said socket tolatch said actuator when said actuator is in either one of saidoperative positions, one of said catches engaging with said detentinside of said socket to resilient deform said latch member for allowingsaid detent to escape outwardly of said socket as said actuator moves bybeing electrostatically attracted to one of said side effectors, therebyenabling said latch member to resiliently return for engagement withsaid catch outside of said socket, said unlatch means comprising arelease lever formed at each of said side effectors to be movabletogether therewith, said release lever being engageable with said leastone latch member to resiliently deform it for releasing said detent fromsaid catch and for allowing said dent to advance into said socket as oneof said side effectors moves towards said actuator by theelectrostatically attracting force.
 12. The system as set forth in claim11, wherein each of said socket is provided in its Interior with aretainer projection spaced inwardly from said catch along said linearaxis, said retainer projection being held close to said detent when saidactuator is in said neutral position, retaining said actuator around itsneutral position in the absence of said electrostatically attractingforce between said actuator and any one of said side effectors.
 13. Anoptical switch comprising: an input optical guide adapted to receive alight signal; two output optical guides each adapted to output saidlight signal; and an actuator system having an actuator carrying amirror for reflecting the light signal incoming through said inputoptical guide to one of said output guides, said actuator systemcomprising: a substrate; an actuator carried on said substrate to bemovable along a linear axis between two operative positions past aneutral position, said actuator being connected to said mirror, saidactuator being formed on its opposite ends respectively with centerelectrodes with respect to said linear axis, and being resilientlysupported to said substrate to be given a spring bias by which saidactuator is biased towards said neutral position; first and second sideeffectors carried on said substrate and disposed respectively onopposite ends of said actuator with respect to said linear axis; saidside effectors being formed respectively with side electrodes that areheld in electrostatically coupling relation with said center electrodes;driving means which develops an electrostatically attracting forcebetween said center electrode and said side electrodes for driving saidactuator into either one of said two operating position; latch meanswhich latches said actuator in one of said operative position againstsaid spring bias when said actuator is moved to said one position, andunlatch means which unlatches said actuator to allow said actuator tomove out of said one operative position towards the other operativeposition, wherein said side effectors are movable towards and away fromsaid actuator along said linear axis between a normal position and ashifted position close to said actuator, said unlatch means isinterlocked with the movement of said side effectors in order to unlatchsaid actuator as one of said side effectors moves to it shiftedposition, thereby allowing said actuator to move out of one of saidoperative position and allowing it to move to the other operativeposition by the electrostatically force developed between said one sideeffector and said actuator.